Intermediate- and heavy-Higgs-boson physics at a 0.5 TeVe+e−collider

We explore the potential of a future ${\mathit{e}}^{+}$ ${\mathit{e}}^{\mathrm{-}}$ collider in the 0.5 TeV center-of-mass energy range to detect intermediate or heavy Higgs bosons in the standard model. We first briefly assess the logistics for finding a Higgs boson of intermediate mass, with ${\mathit{M}}_{\mathit{Z}}$<${\mathit{m}}_{\mathit{H}}$<2${\mathit{M}}_{\mathit{W}}$. We then study in detail the possibility of detecting a heavy Higgs boson, with ${\mathit{m}}_{\mathit{H}}$>2${\mathit{M}}_{\mathit{W}}$, through the production of pairs of weak bosons. We quantitatively analyze the sensitivity of the process ${\mathit{e}}^{+}$ ${\mathit{e}}^{\mathrm{-}}$→νν¯${\mathit{W}}^{+}$ ${\mathit{W}}^{\mathrm{-}}$(ZZ) to the presence of a heavy-Higgs-boson resonance in the standard model. We compare this signal to various backgrounds and to the smaller signal from ${\mathit{e}}^{+}$ ${\mathit{e}}^{\mathrm{-}}$→ZH→${\mathrm{\mu }}^{+}$ ${\mathrm{\mu }}^{\mathrm{-}}$ ${\mathit{W}}^{+}$ ${\mathit{W}}^{\mathrm{-}}$(ZZ), assuming the weak-boson pairs to be detected and measured in their dominant hadronic decay modes ${\mathit{W}}^{+}$ ${\mathit{W}}^{\mathrm{-}}$(ZZ)→4 jets. A related Higgs-boson signal in 6-jet final states is also estimated. We show how the main backgrounds from ${\mathit{e}}^{+}$ ${\mathit{e}}^{\mathrm{-}}$ ${\mathit{W}}^{+}$ ${\mathit{W}}^{\mathrm{-}}$(ZZ), eνWZ, and tt¯ production can be reduced by suitable acceptance cuts. Bremsstrahlung and typical beamstrahlung corrections are calculated. These corrections reduce Higgs-boson production by scattering mechanisms but increase production by annihilation mechanisms; they also smear out some dynamical features such as Jacobian peaks in ${\mathit{p}}_{\mathit{T}}$(H). With all these corrections included, we conclude that it should be possible to detect a heavy-Higgs-boson signal in the νν¯${\mathit{W}}^{+}$